1. Field of the Invention
The present invention relates generally to a process for the wet treatment of textile materials. More particularly, the invention relates to a process for cleaning, bleaching, scouring, dyeing, fixing and the like of textile materials having capillary-active properties by means of chemicals dissolved in a liquid. The textile material to be treated is present in the form of loose fibers, yarn or piece goods. The liquid filled into a vessel is intermittently or alternately moved and thereby caused to act on the textile material by means of essentially only a partial evaporation which is regulated by a controlled pressure reduction in the vessel. A pulsating motion is imparted to the liquid while it acts on the textile material by the introduction of a gaseous medium.
2. Description of the Prior Art
In bleaching textile material, the material is discolored, particularly by means of oxidation or reduction. The chemicals and the process technology utilized must carefully be adjusted to the materials to be treated. Since many chemicals quickly decompose when they are, for example, heated, stabilizers are required for slowing down the disintegration. However, these stabilizers make bleaching expensive and complicated.
A process in which an undyed or uncolored material is colored or in which a colored material is given a different color is generally called dyeing. The dye is transferred to the material by adsorption at the surface, by diffusion, by formation on or in the fiber, or by chemical reaction. The treatment is predominantly effected in aqueous solutions or in suspensions of dyes with the addition of dyeing auxiliaries, such as, wetting agents, salts, alkalies, acids etc. The dyeing process is carried out by either moving the material through the motionless liquor or by causing the liquor to flow through the material.
Specific dyeing processes are the jet process, the high temperature process, the pad-roll process, the pad-steam process, the stand-fast process and the thermosol process.
Also known is the foam dyeing process. However, this process is utilized less frequently. In this process, bubbles are generated in the liquor by the addition of foaming agents. These bubbles are utilized for transferring to the material to be dyed specific dyes whose molecules have hydrophilic as well as hydrophobic ends.
In addition, dyeing processes are known which utilize solvents other than water. Usually volatile hydrocarbons are used. However, these processes are not used in practice because of the harmful, frequently even toxic or explosive, properties of the solvents.
It is the object of all dyeing processes to obtain a bond between the dyes and the material to be dyed utilizing means which are as inexpensive and uncomplicated as possible. The durability and stability of this bond is an essential measure of the degree of fastness of the dyeing. The procedures which are carried out for dyeing are partially of a chemical and partially of a physical nature. Particularly in capillary-active fibers, physical processes on the basis of capillary and osmotic forces clearly predominate. The best known representatives of capillary-active fibers are wool and cotton, however, synthetic fibers may also be included. The capillary and osmotic forces act equally during cold dyeing or hot dyeing, during discoloring as well as during bleaching.
Most of the bleaching and dyeing processes require a large amount of time and energy. The liquor and/or the material must be uniformly moved. Especially the temperature must be adjusted to the correct value. Frequently a temperature increase during the process of up to more than 100.degree. C. is required.
No. DE-A-27 14 802 discloses a dyeing process for textile materials consisting of natural fibers or synthetic fibers or mixtures thereof. In this process, dyeing is carried out under negative pressure. The temperature of the liquid is maintained at the boiling point for about 10 minutes with the prevailing negative pressure being taken into consideration. Subsequently, pressure and temperature are quickly increased and dyeing of the textile material is concluded by means of the conventional process. In this known process, a more intensive dyeing is expected to result, while the treatment time is shorter and the energy required is reduced. This result is essentially due to the fact that the vacuum sucks off a large part of the air which usually prevents moistening of the textile material with liquid. The treatment of the material is careful because of the reduced temperature and the reduced duration of the process. In addition, a better utilization of the dyes was observed. By reducing the portion of air contained in the treatment vessel, it is also possible to process with fewer problems dyes which are sensitive to certain gaseous components in the air.
No. EP-B-22 572 discloses another process for the treatment of textile materials under vacuum. In this process, the liquid is moved and thereby caused to act on the textile material essentially exclusively by local partial evaporation due to a controlled pressure reduction in the treatment vessel. The entire dyeing process takes place under vacuum. Dyeing under normal pressure with simultaneous pumping of the liquid is not intended. Since the liquid cools off during the continuous partial evaporation, the liquid is continuously reheated. This reheating is preferably effected by a direct introduction of vapor. Due to the negative pressure in the treatment vessel, an explosive expansion of the vapor bubbles introduced into the liquid takes place. As a result, a pulsating motion is additionally imparted to the liquid. On the other hand, these explosions are so strong that sensitive materials, for example, yarns wound onto bobbins, may be destroyed. The vapor which is introduced increases the temperature of the liquid, so that the evaporation increases and the vacuum collapses unless a very powerful and, thus, expensive vacuum pump is used.
Another disadvantage of the known process resides in the fact that commercially used vapor usually is contaminated, particularly with iron. Many dyes, particularly the indanthrene dyes, are negatively influenced or even destroyed by vapor. Therefore, the known process can only really be used for a relatively small number of dyes.
Finally, it should be pointed out that the vapor supplied at least partially condensates to water, so that the treatment liquid becomes thinner. Consequently, the treatment times are increased and the treatment results become poorer. Furthermore, a formation of foam, as it is desired in some cases, does not occur.
It is, therefore, the primary object of the present invention to provide a process of the afore-mentioned type which is quick, energy-saving and inexpensive. In addition, the textile material is to be subjected to a careful treatment. Also, a particularly simple and effective control of the process conditions is desired.